1. Field of the Invention
The present invention relates to a drive transmission system for a vessel propelling equipment such as an outboard motor, aboard-outboard motor and so forth in which power is transmitted through a clutch.
2. Description of the Related Art
In most of vessel propelling equipment, output power of an engine is transmitted downward by means of a vertical shaft to a propeller shaft. There is provided a clutch mechanism between the vertical shaft and the propeller shaft. The clutch mechanism is composed of two bevel gears rotatably supported or the propeller shaft and driven by the vertical shaft to rotate in opposite directions to each other, and a clutch gear rotatable together with the propeller shaft and slidable along the propeller shaft. The clutch gear is engaged with either bevel gear according to its sliding direction to rotate the propeller shaft in a normal direction or a reverse direction.
In a vessel propelling equipment disclosed in Japanese Patent Laid-Open No. Sho 50-21493, the above-mentioned clutch gear is connected to an annular member axially slidably fitted around the propeller shaft by means of a slider so that the, clutch gear can be slided by sliding the annular member. The annular member is provided with a groove on the periphery and an engaging pin eccentrically hanging down from a lower end of a vertical manipulating shaft (shift rod) is engaged with the groove.
With the rotation of the shift rod the engaging pin rocks back and forth to move the annular member back and forth, thus operating the clutch.
Since the annular member, however, rotates normally and reversely at a high speed together with the propeller shaft, with the engaging pin in the lower part of the shift rod engaging and sliding in contact with the groove in the outer periphery of the annular member, and the annular member is pressed back and forth by the engaging pin while rotating at a high speed, deviation of the shaft center and vibration of the shaft, if slight, are likely to exercise influence on the operation. It is, therefore, necessary to be greatly careful in manufacturing and mounting a support structure of an operation system in order to insure reliable operation of the drive transmission system.
Japanese Patent Laid-Open No. Sho 57-160796 discloses anothe outboard motor. FIG. 16 shows the lowermost part of the outboard motor. On a propeller shaft 01 having a propeller (not shown) fitted at the rear end are rotatably supported a front driven gear 03 and a rear driven gear 04. These driven gears 03, 04 are bevel gears meshed with a drive gear (not shown) fitted to a lower end of a vertical shaft which is an output shaft of an engine (not shown). Rotation of the vertical shaft is transmitted to the driven gears 03, 04, and the driven gears 03, 04 rotate in opposite direction to each other.
A clutch gear 06 is fitted on the propeller shaft by splines between the driven gears 03, 04. In FIG. 16, the clutch gear is positioned at its neutral position. When the clutch gear 06 slides forward and meshes with clutch teeth of the driven gear 03, rotation in the normal direction of the driven gear 03 is transmitted to the propeller shaft 01 and a forward thrust is generated by the propeller. On the other hand, when the clutch gear 06 slides rearward to mesh with clutch teeth of the driven gear 04, rotation in the revese direction of the driven gear 04 is transmitted to the propeller shaft 01 to generate a rearward thrust.
Sliding of the clutch gear 06 is caused by a manipulating shaft 07. The manipulating shaft 07 is connected to the clutch gear 06 by means of a cam 08 fitted to the lower end of the manipulating shaft 07, a cam follower 09 engaging with the cam 08 to move back and forth, a shift slider 010 connected to the cam follower 09 and inserted within the propeller shaft axially slidably, and a clutch shifter pin 011 passing through elongate holes of the shift slider 010 and the propeller shaft 01 perpendicularly and fitted to the clutch gear 06, in turn.
The shift slider 010 is formed in a cylindrical shape, within which to springs 012, 013 are inserted putting the clutch shifter pin 011 between them. The clutch gear 06 is positioned at the neutral position by a set pin provided on the spline fitting position between the clutch gear 06 and the propeller shaft
When the manipulating shaft 07 is manipulated to rotate the cam 08 and wove the shift slider 010 together with the cam follower 09 forward, for example, in the beginning the clutch gear 06 and the clutch shifter pin 011 are held to the neutral position by the set pin and the rear spring 013 is compressed.
Then, at the time when the force of the spring 013 exceeds the holding force by the set pin, the set pin releases the clutch shifter pin 011 and the force of the spring 013 acts on the clutch gear 06 through the clutch shifter pin 011 to cause a snap action, what is called detent action, of the clutch ear 06 forwardly. The clutch teeth of the clutch gear 06 meshes with the clutch teeth of the front driven gear 03 smoothly, the propeller shaft 01 and the propeller integrally fitted to the shaft 01 rotate in the normal direction and tile vessel goes ahead.
On the other hand, when the shift slider 010 moves rearward, the front spring 012 is compressed and the clutch gear 06 meshes with the rear driven gear 04 by the detent action to rotate the propeller shaft 01 and the propeller in the reverse direction so that the vessel goes astern.
Though a smooth clutch engagement can be achieved by the detent action as described above, the above customary detent construction requires two springs 012, 013, and a special jig is necessary when the clutch shifter is assembled, in order to hold the springs 012, 013 in compressed conditions for example, therefore the assembling is not easy.